This invention relates to a separating apparatus and more particularly but not exclusively to an apparatus for separating oil and water from a mixture thereof.
The invention has been developed particularly but not exclusively for separating oil and water from condensate from an air compressor machine, but may be used in other applications for separating from a liquid mixture, two liquid components of differing density.
To comply with legislation it is a requirement that before condensate from an air compressor machine can be disposed of into for example, a drain, or onto the ground, oil has to be removed as required to reduce the contamination to less than 20 parts per million (ppm).
Separating devices are known which collect the condensate in a settling tank which includes a weir over which the lighter oil component is intended to flow, whilst the heavier mainly water component passes towards the bottom of the tank from where it is discharged. The mainly water component is then subjected to filtering for example, to remove any entrained matter and residual oil.
However where the mixture of oil and water form a thick emulsion some of the oil is in solution, such weir devices do not operate well. This is because the thick xe2x80x9cmayonnaisexe2x80x9d like consistency mixture floats on the heavier mainly water component with a substantial proportion of the xe2x80x9cmayonnaisexe2x80x9d, below the surface of the mainly water component. Thus this does not easily pass over the weir. Thus the vessel becomes filled with xe2x80x9cmayonnaisexe2x80x9d consistency mixture which eventually may flow from the vessel with the mainly water component and contaminate the filter.
It has been proposed to protect the filter, which typically is a carbon filter, by the use of an oleophillic material e.g. contained in a bag. However the amount of oleophillic material which has been used has been small such that the primary separating device has been the weir, and the oleophillic material can quickly become overloaded leaving the filter susceptible to blockage.
According to one aspect of the invention we provide an apparatus for separating from a liquid mixture, first and second liquid components, wherein the first liquid component has a greater density than the second liquid component, the apparatus including a vessel having an inlet through which the mixture is introduced into the vessel, and an outlet through which separated first liquid is in use discharged, and there being a separating member within the vessel, the mixture being constrained to contact the separating member, the separating member including a material which adsorbs the second liquid component characterised in that the separating member is adapted to move in the vessel downwardly in response to an increase in the weight thereof as second liquid component is adsorbed.
Such an apparatus has been found to be very efficient at separating the first and second liquid components. Because the separating member moves downwardly in the vessel as the adsorbing material adsorbs second liquid component, material which is unsaturated with second liquid component may continuously be presented at the surface of the liquid in the vessel, where the lighter second liquid component tends to settle. When the separating member has moved down in the vessel to a low position, having adsorbed a maximum volume of the second liquid material, the separating member, or at least the adsorbing material, may be disposed of.
The inlet may be positioned above the outlet so that liquid flows through the vessel under gravity. In one embodiment the inlet is positioned above the separating member, and the outlet is positioned towards a bottom of the vessel. Thus the mixture passes down through the adsorbing material. Some of the second liquid is likely to be adsorbed during this passage.
Preferably therefore the inlet is positioned at a height between a top and bottom of the vessel generally at a level at which a lower part of the separating member is located prior to any second liquid being adsorbed thereby.
Thus the heavier first liquid component will pass downwardly through separating member which may already have adsorbed second liquid component, whilst the adsorbing material of the separating member above the inlet will be unsaturated.
In each case, the outlet of the vessel may be connected to an upwardly extending chamber which has an outlet for the first liquid component, the liquid level in the vessel being governed by the height of the outlet from the chamber. Thus mixture may be continuously or intermittently introduced into the vessel through the inlet, with a commensurate volume of first liquid component flowing from the outlet from the chamber, so that there is no risk of overfilling the vessel, i.e. the surface of the liquid in the vessel is maintained at a constant level.
In a preferred embodiment the upwardly extending chamber includes a filter means such as a carbon filter, for filtering from the first liquid component any entrained matter and/or residual second liquid component. However if desired, a filter means may be provided in the vessel between the separating member and the outlet.
In one arrangement the separating member is adapted to float in the vessel at a level determined by the volume of second liquid adsorbed thereby. To compensate for the weight of the separating member itself, to ensure that no or a minimal amount of the separating member is submerged in the liquid in the vessel prior to any second liquid component being adsorbed by the adsorbing material, thereby, the separating member may include a float to increase the buoyancy of the member. Thus initially the separating member floats so that a lower part thereof is at a desired height in the vessel, e.g. at the level of the inlet.
As an alternative to a float, any other support means may be provided, such as a spring means or counterbalance, to support the separating member in the vessel so that prior to the adsorbing material of the separating member adsorbing second liquid component, a lower part of the separating member is at a desired height in the vessel.
The adsorbing material of the separating member may be oleophillic such that the separating material is active to adsorb from a liquid mixture of oil and water, oil, for example oil contained in a liquid mixture being liquid condensate from an air compressor machine.
According to a second aspect of the invention we provide a method of separating from a liquid mixture, first and second liquid components, wherein the first liquid component has a greater density than the second liquid component, the method including introducing into a vessel through an inlet thereof the mixture, constraining the mixture to contact a separating member in the vessel, which member includes a material which adsorbs the second liquid component, and discharging from the vessel through an outlet thereof separated first liquid component, characterised in that the separating member is adapted to move in the vessel downwardly in response to an increase in the weight thereof as second liquid component is adsorbed thereby, and mixture is introduced into the vessel until the separating member has moved to a low position in the vessel.
The method may include filtering any entrained matter and residual second liquid component from the separated first liquid subsequent to contacting the mixture with the adsorbing material of the separating member. For example the separated first liquid component may be discharged from the vessel prior to filtering.
The liquid level in the vessel may be controlled by the level of an outlet from an upwardly extending chamber which is connected to the vessel outlet.